(a) Field of the Invention:
The present invention relates to magnetic head having a ferrite pole pieces and thin film coils.
(b) Related art statement:
Most of the conventional magnetic heads using the ferrite core are of a structure in which a wire is wound on a ferrite core piece.
Recently, however, the magnetic head core and coil have been designed increasingly compact because increased write/read efficiency of the magnetic head and smaller width of magnetic head track are required to meet the requirements for high recording density and track density. In these circumstances, the conventional types of magnetic head with the wire wound on the ferrite core piece cannot meet such requirements.
To meet the above-mentioned requirements, various proposals have been made. One of such proposals is disclosed, for example, in the Japanese Unexamined Patent Publication (Kokai) No. 57-78615 (corresponding in U.S. Pat. No. 4,375,657 issued on Mar. 1, 1983).
A magnetic head of such type is shown in FIGS. 1 and 2.
As shown in FIG. 1, the magnetic head has a ferrite substrate 10 and ferrite closure 12. The ferrite substrate 10 is recessed at 14 by photolithography or reactive ion etching. The surface of the ferrite substrate 10 including this recess 14 is covered with a thin film insulative layer 20 of aluminum oxide, and the insulative layer 20 within the recess 14 has formed thereon a coil 16 having two narrow sections 18a and 18b and a wide section 18. The ferrite closure 12 is bonded to the ferrite substrate 10 and these form together a single magnetic head 10. Also, as shown in FIG. 2, the ferrite substrate 10 has provided around it glass layers 30 and 32 which prevent any cross-talk between successive head elements and also define the track width. A recording medium is indicated at 26.
In the above-mentioned conventional techniques, head dissipation I.sup.2 R due to the flow of a recording current I can be limited by increasing the section area of the conductive coil 16 and reducing the electrical resistance R. Also, the conventional technique is advantageous in that a magnetic head of high write/read efficiency can be provided by disposing the conductive coil 16 sufficiently near the magnetic transducing gap 21. On the other hand, since the apex angle near the transducing gap 21, namely, an angle .theta. formed by the inner surface extending from the upper end of the recess 14 with respect to the direction of depth of the transducing gap 21, has a large influence on the transducing efficiency of the magnetic head, the angle .theta. must be maintained an optimal one with which the transducing efficiency of the magnetic head can be maximized, when the recess 14 where the conductive coil 16 is disposed is formed. In the actual production of the magnetic head of such type, a number of ferrite substrates 10 are produced from a single wafer, and the recess 14 for each of the ferrite substrates 10 is formed by photolithography or reactive ion etching under the same conditions before the wafer is cut into the ferrite substrates 10. So, the nonuniformity of the angle .theta. is small within a same lot of the production. However, to form the recess 14 in such a manner as to maintain the angle .theta. constant among the plural lots of ferrite-substrate production and for uniform performance of the magnetic heads thus massively produced, highly advanced technology and process control are required along with the photolithography and reactive ion etching.